Autoflowering vs. Photoperiod: Which Is Better?

When you grow your own weed, much of the enjoyment is the anticipation you feel. You can’t wait to harvest your crop and enjoy your dank buds.

Some of the enjoyment is based on knowing what to expect. You’ve chosen the cannabis strain you want to raise. You can almost taste and smell the flower as it grows, while you imagine the type of high you’ll experience.

But choosing a strain doesn’t only mean deciding between indicas and sativas. There’s another big question to answer: autoflowering or photoperiod?

Those new to growing may have automatically selected their favorite strain without even thinking about that question. But when you grow autoflowering plants, the process is easier to navigate — and you’ll be enjoying your weed months sooner than if you had chosen a photoperiod strain.

Let’s shed some light on the subject.

The Difference between Autoflowering and Photoperiod Plants

The most important environmental factor affecting cannabis plants is light. The reason is simple.

Over many centuries of growing outdoors, the plants have learned to switch from the vegetative stage to the flowering stage when fall approaches and they’re getting less and less sunlight. Indoor growers simulate that effect and trigger the flowering stage (when buds grow) by reducing the amount of light their plants receive.

Since light is the signal for those plants to begin flowering, they’re referred to as “photoperiod” plants. Most strains are photoperiod, which is why beginning growers may not even be aware that there’s an alternative.

There is. Autoflowering plants do just what their name says. They automatically switch from the vegetative stage to the flowering stage after a certain number of weeks of growing, regardless of light conditions.

Where Do Autoflowers Come From?

The autoflowering plants you can grow in your garden don’t occur naturally in the wild. They’re created by cultivators who breed a regular strain with a plant that most people aren’t aware of, cannabis ruderalis. Every reader has certainly heard of indica and sativa, but ruderalis is the third family of weed plants.

The reason ruderalis plants don’t get much love is that they have low levels of THC. They do have another important property, though: they’ve learned to automatically flower three to six weeks after entering the vegetative stage. Experts believe that’s because they originated in colder climates where there are short summers and long periods of daylight.

Ruderalis plants bring one other benefit to the table as well. They make up for their lack of high THC levels with substantial CBD content, making them a good choice for many medical marijuana patients.

However, here’s the main reason that breeders love cannabis ruderalis. When they’re bred with indicas or sativas their genetics can turn the resulting plants into autoflowering strains. The new strain retains most of the THC content of the indica or sativa parent, along with much of the CBD content of the ruderalis parent. And the hybrids gain the ability to flower regardless of the level of light they’re exposed to.

Why would growers want plants that automatically switch to the flowering stage after 3-6 weeks of vegetative growth? It’s primarily because autoflowering drastically reduces the amount of time it takes to grow and harvest weed plants. Photoperiod plants generally need 7-10 weeks just to finish the flowering stage; autoflowers complete their entire growth cycle in that same amount of time.

There are other benefits to choosing autoflowering plants — as well as some drawbacks. It’s important to consider all of them before making a decision.

Pros of Growing Autoflowering Plants

We’ve already discussed the biggest advantage: how quickly autoflowers can be harvested.

There are several others worth mentioning.

• Autoflowers are usually small plants and only reach 2-3 feet in height since their ruderalis parents are small as well. That makes them a good choice for grow rooms without much space. It also makes them ideal for “stealth” grows.
• Autoflowers are easier to grow than photoperiod plants since there’s no need to carefully regulate the amount of light they get.
• Autoflowers can be planted outdoors at any time of the year as long as the climate is conducive to their growth since it doesn’t matter how much daylight is available.
• Autoflowers’ short growth cycle means more plants can be grown and harvested each year.
• Autoflowers are able to survive and thrive with fewer nutrients because of their genetic heritage and their short growing season.
• Autoflowers are usually higher in CBD content.

Cons of Growing Autoflowering Plants

So why doesn’t every grower choose autoflowers? There are some very good reasons to opt for photoperiod strains instead.

• Autoflowers may contain less THC. They usually top out at 20-25% THC content, while photoperiod plants may contain 30% THC or even more. That’s a much smaller difference than it was just 20 years ago, though.
• Autoflowers produce less harvestable flowers than photoperiod plants, because of their smaller size and the shorter amount of time they have to grow. (However, it’s possible to make up for that deficit, because more autoflowering plants can fit into the space needed to grow a few large sativas.)
• Autoflowers are often sturdier plants because of their genetics, but they have less time in their growing cycle to recover from environmental stressors. Even topping or training autoflowering plants can badly damage them. Maintaining “perfect” growing conditions is a must with autoflowering plants.

Here’s the bottom line. Commercial growers and most accomplished home growers prefer photoperiod plants because they want the higher yields of more potent buds — and they’re experienced enough to deal with the greater challenges of growing them.

Can You Make Your Own Autoflowering Plants?

Probably not. Definitely not, if you’re planning to grow clones.

Here’s the one “odd” thing about autoflowers: when you clone them, they take on the age of their parent. In other words, if you clone an autoflower the seedling will already be weeks old and it will produce a very small harvest because its growth will have been stunted.

You probably won’t be able to breed autoflowers, either. You’ll need a ruderalis plant in order to do it, and pure ruderalis seeds are very hard to come by.

The only realistic way to grow autoflowers is to purchase autoflowering seeds. And yes, you can purchase feminized autoflower seeds to ensure that you don’t have to worry about eliminating male plants from your grow.

Autoflowering vs. Photoperiod Cannabis: FAQ

Q: Won’t there be much less choice in strains if you want to grow autoflower plants?
A: Yes, but you’d probably be surprised by how many well-known, popular strains have been bred in autoflower form. White Widow, Gorilla Glue, GSC, Blueberry, and Amnesia Haze are just a few of the strains that you might “want” to grow, which are also available as autoflowering seeds.

Q: How much smaller than a photoperiod harvest would an autoflower harvest be?
A: If each is grown under ideal conditions, a typical autoflower plant will produce about two-thirds the amount of flower you’d get from a similar photoperiod plant. Remember, though, you can probably fit more autoflowers into your grow space, and you can grow and harvest two autoflower crops in the time it would normally take to grow a single crop of photoperiod plants.

References

• Petit, J., Salentijn, E. M., Paulo, M. J., Denneboom, C., & Trindade, L. M. (2020). Genetic architecture of flowering time and sex determination in hemp (Cannabis sativa L.): a genome-wide association study. Frontiers in plant science, 1704. [1]
• Gloss, D. (2015). An overview of products and bias in research. Neurotherapeutics, 12(4), 731-734. [2]